JP6375097B2 - Radiation treatment planning apparatus and treatment planning method - Google Patents

Description

  The present invention relates to a radiation therapy planning apparatus and a therapy planning method.

  In radiation therapy, treatment is performed by irradiating a target tumor cell with radiation. X-rays are the most widely used treatment using radiation, but there is also a demand for treatments using particle beams (charged particle beams) typified by proton beams and carbon beams with high dose concentration to the target. It is growing.

  In radiotherapy, excessive irradiation and insufficient dose can lead to side effects on normal tissues other than tumors and tumor recurrence. It is required to irradiate the tumor area with the dose specified to concentrate as much as possible and as accurately as possible.

  In the treatment using X-rays called IMRT (Intensity Modulated Radiation Therapy), even if the target area with a complicated shape is irradiated by irradiating it from multiple directions while changing the shape of the collimator, the surrounding normal tissue is irradiated. Doses can be minimized. IMPT (Intensity Modulated Proton Therapy), which forms a uniform dose distribution in a target region by irradiating a number of thin beams with adjusted intensities from a plurality of irradiation angles, also in the treatment using particle beams.

  The IMPT is realized using a scanning method. The scanning method is a method in which a thin charged particle beam is deflected by two sets of scanning magnets and guided to an arbitrary position in the plane to irradiate the tumor so that it fills the inside of the tumor, giving a high dose only to the tumor area. And various distributions can be easily formed.

  In IMRT and IMPT, the process of creating a plan using a radiotherapy planning device before actual irradiation is extremely important. The radiation treatment planning apparatus simulates the dose distribution in the patient body by numerical calculation based on the information in the patient body obtained from the CT image or the like. The operator determines the irradiation conditions such as the irradiation direction, energy, irradiation position, and irradiation amount while referring to the calculation result of the radiation therapy planning apparatus. The general process is briefly described below.

  The operator first inputs a target area to be irradiated with radiation. A CT image is mainly used, and a target region is input to each slice of the image. The input data is stored in the memory on the radiation treatment planning apparatus as three-dimensional area data when the operator registers it in the radiation treatment planning apparatus. If necessary, enter and register the position of the vital organ in the same way.

  Next, the operator sets a prescription dose that becomes a target dose value for each registered region. The setting is made for the previously registered target area and important organ. For example, in the target area, a dose sufficient to necrotize the tumor is specified. In many cases, the minimum and maximum doses to be delivered to the target area are specified. On the other hand, for important organs, an allowable dose is determined as the maximum tolerable dose value.

  The beam irradiation position and dose for realizing the dose distribution designated by the operator are determined by the radiation therapy planning apparatus. Usually, the irradiation position is determined first, and then the irradiation dose is determined so as to satisfy the dose distribution condition input by the operator.

  As a method for efficiently determining an irradiation amount, a method using an objective function in which a deviation from a prescription dose is quantified as described in Non-Patent Document 1 is widely adopted. The objective function is defined so that the dose distribution becomes smaller as the prescription dose is satisfied, and the optimum dose is calculated by searching for the dose that minimizes the dose distribution by iterative calculation.

  As a result, it is possible to calculate an irradiation dose that obtains a dose distribution satisfying the prescription dose. However, as described in Non-Patent Document 2 and Non-Patent Document 3, patient positioning uncertainty (positioning error) or due to breathing There are many uncertainties such as target movement (breathing movement error) and uncertainty (range error) when converting CT values to water equivalent thickness.

  Due to the uncertainty described above, there is a possibility that the dose distribution in the patient when actually irradiated does not match the dose distribution of the planned treatment plan. In particular, in IMRT and IMPT, since a desired dose distribution is formed by forming and adding non-uniform dose distributions from a plurality of irradiation directions, the influence of these uncertainties can be significant.

  In order to reduce the influence of uncertainty at the time of treatment planning, several methods have been proposed that focus on characteristics other than the difference between the dose of each region (target region and important organ) and the prescription dose. For example, in Non-Patent Document 4, it is assumed that the range of the beam irradiated to the target changes randomly, the dose and the objective function value given by the beam are calculated, and the optimization calculation is performed. Reduce the sensitivity of the dose distribution to the uncertainty of In Non-Patent Document 5, a dose distribution when a positioning error occurs in addition to a range error is calculated under a plurality of conditions, and information on the maximum deviation between the calculated dose in each region and the prescription dose is used as an objective function. In addition to the above item, optimization calculation reduces the maximum deviation between the dose in each area and the prescription dose when range error and positioning error occur, and the range and positioning uncertainty. The sensitivity of the dose distribution to

A. Lomax, “Intensity modulation methods for proton radiotherapy” Phys. Med. Biol. 44 (1999) 185-205. A. Lomax, “Intensity modulated proton therapy and its sensitivity to treatment uncertainties 1: the potential effects of calculation uncertainties” Phys. Med. Biol. 53 (2008) 1027-1042 A. Lomax, “Intensity modulated proton therapy and its sensitivity to treatment uncertainties 2: the potential effects of inter-fraction and inter-field motions” Phys. Med. Biol. 53 (2008) 1043-1056 J. Unkelbach et al., “Accounting for range uncertainties in the optimization of intensity modulated proton therapy” Phys. Med. Biol. 52 (2007) 2755-2773 D. Pflugfelder et al., “Worst case optimization: a method to account for uncertainties in the optimization of intensity modulated proton therapy” Phys. Med. Biol. 53 (2008) 1689-1700

  On the other hand, the sensitivity to the uncertainty of the plan can also be reduced by suppressing the irradiation to the area that is empirically determined that the influence of the uncertainty is large. For example, if the operator can determine that the range error is large in a region where the density change is large, such as a portion where a metal artifact is generated or a region near a bone, a treatment plan in which irradiation to the region is suppressed may be created.

  Here, there is a possibility that a dose distribution greatly deviating from the prescription dose is obtained by simply suppressing the dose in a certain region. Therefore, the radiotherapy planning apparatus needs to create a plan that suppresses the dose to a specific region as much as possible while bringing the dose distribution close to the prescription dose. However, the conventional radiotherapy planning device was able to control the dose distribution to approach the target, but the treatment planning device with the function to directly control the dose to a specific area during the optimization calculation Never before.

  In the radiotherapy planning apparatus for creating the treatment plan information for performing radiotherapy, the above-mentioned problem is performed by the operator based on the input result of the input device and the input device for inputting the prescription dose, the irradiation angle, and the like, A calculation device that determines the irradiation conditions so that the dose distribution approaches the prescription dose, creates treatment plan information, and a display device that displays the treatment plan information. The calculation device controls the dose that is determined by the radiation irradiation position. This can be solved by a radiation therapy planning apparatus characterized in that an index representing the degree of demand for the above is set for each irradiation position and the dose is controlled using the index when determining the irradiation condition.

  According to the present invention, it is possible to create an irradiation condition that suppresses deterioration of dose distribution in a patient due to uncertainty in treatment planning.

It is a figure showing the flow until a treatment plan is drawn up by suitable one Embodiment of this invention. It is a figure showing the flow of a process of this invention apparatus in suitable one Embodiment of this invention. It is explanatory drawing which shows the structure of the treatment plan apparatus which is preferable one Embodiment of this invention. It is a figure explaining the input of the target area | region and important organ within the slice of CT data. It is explanatory drawing which shows the procedure of the selection method of the spot position in embodiment. It is explanatory drawing which shows the procedure of the calculation method of the water equivalent depth in the arbitrary positions of CT data in embodiment. It is explanatory drawing which shows the procedure of the method of calculating the information of the stop position of the particle beam in embodiment. It is explanatory drawing which shows the procedure of the calculation method of the score regarding the positioning error to the target area | region in embodiment. It is explanatory drawing which shows the procedure of the calculation method of the score regarding the range error to the important organ in embodiment. It is the figure which displayed the stop position of the beam on the patient CT data on the display device. The size of the point in the figure represents the size of the score set for each spot.

  Embodiments of a radiation treatment planning apparatus and a treatment planning method of the present invention will be described below with reference to the drawings.

  A radiotherapy planning apparatus 301 of this embodiment will be described with reference to FIGS. 1 to 3. The treatment planning apparatus 301 of the present embodiment will be described on the premise of a treatment plan of particle beam treatment by scanning irradiation method, but also when creating a treatment plan of radiation treatment using other radiation such as X-rays and gamma rays. Adaptable.

  FIG. 1 is a diagram showing a flow of treatment planning when a radiation treatment planning apparatus (hereinafter, treatment planning apparatus) 301 according to the present embodiment is used. FIG. 2 is a diagram showing the flow of processing of the treatment planning apparatus 301 of the present embodiment, and is a diagram showing in detail step 105 of FIG. 1 (automatic calculation step of the treatment planning apparatus). FIG. 3 is a diagram illustrating an overall configuration of the treatment planning apparatus 301.

  As shown in FIG. 3, the treatment planning apparatus 301 includes an input device 302, a display device 303, a memory 304, an arithmetic processing device 305, and a communication device 306. An arithmetic processing device 305 is connected to the input device 302, the display device 303, the memory (storage device) 304, and the communication device 306. The treatment planning apparatus 301 is connected to the data server 307 via a network. Specifically, the communication device 306 of the treatment planning device 301 is connected to the data server 307 via the network and exchanges data.

  A patient to be treated has previously taken a CT image for treatment planning using a CT apparatus. Data (CT data) related to the CT image for treatment planning imaged by the CT apparatus is stored in the data server 307. This CT data is three-dimensional data in which CT values are recorded for each small area called a voxel. The treatment planning apparatus 301 makes a treatment plan using this CT data.

  When a medical worker (engineer or doctor) who is an operator inputs patient information (patient ID) from the input device 302, the treatment planning device 301 starts creating treatment plan information of the patient corresponding to the patient ID (step) 101). First, the input device 302 outputs the input patient ID to the arithmetic processing device 305. The arithmetic processing unit 305 reads CT data of the target patient from the data server 307 based on the input patient ID. That is, the treatment planning apparatus 301 receives the CT data of the patient corresponding to the patient ID from the data server 307 through the network connected to the communication apparatus 306 and stores it in the memory 304. Further, the treatment planning apparatus 301 creates a CT image for treatment planning based on the received CT data, and displays it on the display device 303. The display device 303 displays an image in each slice (each layer) obtained by dividing the region including the affected area of the patient into a plurality of layers.

  The operator inputs an area (target area) to be designated as a target for each slice of the CT image using the input device 302 (device such as a mouse) while checking the CT image displayed on the display device 303. To do. The target area is an area that is determined to be irradiated with a particle beam, for example, including an area that the operator has determined to be a tumor area of a patient. When the input of the target area for all slices is completed, the operator inputs an input end signal from the input device 302. When receiving the input end signal, the treatment planning apparatus 301 stores and registers the information of the target area in all slices in the memory 304 (step 102). Information registered in the memory 304 is three-dimensional position information indicating the target area input by the operator. If there is an important organ in the vicinity of the target area where the irradiation dose should be suppressed as much as possible, or if there is another area that needs to be evaluated or controlled, the operator can select these based on the image information displayed on the display device 303. The position information of the important organs is input from the input device 302. The position information of the important organs and the like is stored and registered in the memory 304 as with the target area information. FIG. 4 shows an example in which the display unit 303 displays the input target region 402 and the region 403 such as an important organ in an arbitrary slice (layer) 401 including the affected part, which is generated based on the CT data.

  Next, the operator designates the irradiation direction. When performing irradiation from a plurality of directions, a plurality of angles are selected. Other parameters for irradiation to be determined by the operator include a dose value (prescription dose) to be irradiated to the region registered in step 102 and an interval between adjacent spots. The prescription dose includes the target dose that should be delivered to the target and the maximum dose that important organs should avoid. The initial value of the horizontal spot interval is automatically determined so as to be approximately equal to the beam size of the charged particle beam, but can be changed by the operator. The operator sets these necessary irradiation parameters (step 103).

  After setting the necessary irradiation parameters, the operator sets an estimated value of uncertainty in planning a treatment plan (step 104). The operator uses the input device 302 to input the magnitude of the estimated uncertainty in mm units or%.

  After the estimated value of uncertainty is set, the treatment planning device 301 performs automatic calculation (step 201). First, the arithmetic processing unit 305 starts selecting an irradiation position from the CT data read into the memory 304 and the region information input by the operator (step 202). A method for selecting a spot position will be described with reference to FIG. At the time of irradiation, it is assumed that the position of the center of gravity of the target region 402 is positioned so as to coincide with the isocenter (rotation center position of the rotary irradiation apparatus (not shown) of the particle beam therapy apparatus) 501. The irradiation position is defined by coordinates on a plane (isocenter plane) 504 that includes the isocenter 501 and is perpendicular to a straight line 503 connecting the scan center point (line source) 502 and the isocenter 501. Hereinafter, the surface 504 is referred to as an isocenter surface, and the straight line 503 is referred to as a beam center axis. As an example, assume that a position on the isocenter plane 504 and a point 505 are selected as irradiation positions in FIG. When the beam is irradiated along the line 506 connecting the source 502 and the point 505, the treatment planning apparatus 301 searches for energy where the position where the beam stops is substantially within the target, and the energy (one type is (Not limited) is selected as the energy applied to the position of the point 505. By performing this for all irradiation positions set on the isocenter surface 504, a set of irradiation positions on the isocenter surface 504 and energy necessary for irradiating the target (hereinafter referred to as spots) can be obtained.

  The irradiation positions on the isocenter surface 504 are selected so that the interval between adjacent irradiation positions is equal to or less than the value specified in step 103. The simplest method is to arrange one side on a square lattice with a specified interval.

  In the treatment planning apparatus 301 of the present embodiment, an index (hereinafter referred to as a score) indicating the degree of demand for dose suppression is set for each spot (step 203). As described above, there are positioning errors and range errors as examples of the uncertainty at the time of treatment planning. The magnitude of the positioning error is about several millimeters or less, and about a few percent for range error. For example, when a positioning error occurs, the range of a spot where a high-density material such as bone exists around the beam passage path greatly varies due to the high-density material, which causes deterioration of the dose distribution in the target area. Therefore, in order to reduce the influence of the positioning error, the score of the spot needs to be set high. Also, a spot where an important organ exists in the vicinity of the beam passage path needs to have a high score in order to increase the dose to the important organ when a positioning error or a range error occurs. In the following, the score calculation method by the arithmetic processing unit 305 will be described with reference to FIGS. 6 to 8 by taking as an example a score related to the positioning error in the target region and a score related to the range error to the important organ.

  First, the arithmetic processing unit 305 of the treatment planning apparatus 301 calculates a water equivalent thickness at an arbitrary position of CT data. A method of calculating the water equivalent thickness will be described with reference to FIG. First, the arithmetic processing unit 305 reads information on the angle at which the charged particle beam is irradiated among the irradiation condition information stored in the memory 304. Subsequently, the arithmetic processing unit 305 defines a surface 601 perpendicular to the straight line 503 connecting the radiation source 502 and the isocenter 501, and divides the surface 601 with an appropriate resolution (usually several mm or less). Each divided area is called a pixel. Subsequently, the arithmetic processing unit 305 performs the voxel of the CT data for each determined step (usually the same size as the pixel 602) along the straight line 603 connecting the center positions of the pixels 602 from the radiation source 502 side. Accumulate values. At this time, the CT value held in each voxel is integrated after being converted into a thickness when the substance in the voxel is converted into water by a table stored in the memory 304 of the treatment planning apparatus 301 in advance. This is called water equivalent thickness. The conversion from the CT value to the water equivalent thickness may be performed collectively before the calculation. The arithmetic unit 305 performs the same calculation for all pixels obtained by dividing the plane 601 perpendicular to the beam traveling direction. By this operation, the water equivalent thickness at an arbitrary position is calculated.

  Subsequently, the arithmetic processing unit 305 calculates the beam stop position of the beam irradiated to the spot. The calculation method will be described with reference to FIG. First, the arithmetic processing unit 305 reads a spot stored in the memory 304. Subsequently, the depth to the beam stop position (position where the peak appears in the dose distribution) is read from the table held in the memory 304 with respect to the read spot energy. The arithmetic processing unit 305 calculates the water equivalent thickness from the radiation source 502 for each determined step (usually the same size as the pixel 602) along the straight line 702 connecting the spot position 701 of the read spot and the radiation source 502. With reference to this, a stop position of the beam and a pixel (beam stop pixel) 703 including the stop position are calculated.

  Using the beam stop position and the beam stop pixel 703 calculated by the above method, the arithmetic processing unit 305 calculates a score for each spot. The case where the score regarding the positioning error to the target area is calculated will be described with reference to FIGS. The arithmetic processing unit 305 calculates a score on a plane 704 having the beam stop pixel 703 and perpendicular to the beam central axis. The arithmetic processing unit 305 reads the positioning error δ [mm] set in advance by the operator. Subsequently, the arithmetic processing unit 305 calculates the difference between the water equivalent depth of the beam stop pixel and each pixel for each pixel on the surface 704 whose distance from the beam stop pixel 703 is δ [mm] or less. The sum of squares is calculated, and the calculation result is temporarily stored in the memory 304 as a spot score. Therefore, if high-density material or low-density material (bone or air) exists only around the beam passage path, the difference in water equivalent thickness on and around the beam passage path is large, and the spot score is large. Become. The arithmetic processing unit 305 calculates the scores for all the spots stored in the memory 304 and then normalizes the scores of all the spots so that the maximum value of the score becomes 1, and then the memory 304 Save to.

  The case where the score regarding the range error to an important organ is calculated is demonstrated using FIG. The arithmetic processing unit 305 calculates a score along a straight line 702 connecting the spot position 701 of the spot read out from the memory 304 by the arithmetic processing unit 305 and the radiation source 502. First, the arithmetic processing unit 305 reads the range error δR [%] set in advance by the operator, and obtains the calculation range δ [mm] from the water equivalent depth of the beam stop pixel 703. Subsequently, the arithmetic processing unit 305 determines whether each pixel exists in the important organ registered in 102 with respect to the pixel 901 on the straight line 503 whose distance from the beam stop pixel 703 is δ [mm] or less. The total number of pixels present in the vital organ is temporarily stored in the memory as a spot score. Therefore, the spot value where the beam stops immediately before the important organ increases. The arithmetic processing unit 305 calculates the scores for all the spots stored in the memory 304 and then normalizes the scores of all the spots so that the maximum value of the score becomes 1, and then the memory 304 Save to.

  The score of the spot calculated by the above method can be visually confirmed. The display device 303 displays the irradiation position for each energy of the irradiation spot. It is also possible to display the beam stop position of the beam applied to the spot superimposed on the CT slice image of the patient. FIG. 10 shows an example in which the beam stop position is superimposed on the slice 401 in the CT data of FIG. 4 on the display device 303 and displayed. Point 1001 represents that the beam irradiated to the spot stops at this position. The score set for each spot can also be displayed by the size or color of the points. In FIG. 10, the magnitude of the score is represented by the point size.

  It is also possible for the operator to create an arbitrary region 1002 using the input device 302 on the display screen on the display device 303 and change the score value of the spot in the created region. For example, when a metal artifact has occurred in the CT data, and the operator empirically determines that there is high uncertainty in the metal artifact generation area, the operator uses the input device 302 to cover the generation area. Create a region to set the score as follows. The operator sets an arbitrary value as a score for the spot where the beam stops within the region. As described above, it is possible to set a score for a plurality of spots at once by specifying a region and setting a score.

  When scores are set for all the spots that have been set, the arithmetic processing unit 305 of the treatment planning apparatus 301 performs an optimization calculation of the dose by an operator's instruction operation. The treatment planning apparatus 301 normally defines an objective function in which the deviation from the prescription dose is quantified (step 204), and minimizes this by iterative calculation to calculate the dose as a parameter of the objective function (step 205). ). In the treatment planning apparatus 301 of the present embodiment, the influence set by the treatment plan is reduced by suppressing the irradiation amount to a specific spot by considering the score set for each spot in the objective function. Let The arithmetic processing unit 305 generates (defines) the objective function as follows.

The arithmetic processing unit 305 sets m and n points for calculating doses in the target region 401 and the important organ 402 registered in step 102. The dose values at these points must satisfy as much as possible the prescription dose entered by the operator in step 103. Here, it is assumed that the target dose value p is set for m points corresponding to the target region 401 and the allowable dose value l is set for n points corresponding to the important organ 402. A vector with each spot dose as an element as a parameter of the objective function
Write.
Is the total number of spots k. Next, a vector whose elements are dose values at m points in the target area 401 is
The amount of irradiation to each spot
Can be expressed by the following (formula 1).

  The matrix A represents the contribution of the beam irradiated to each spot to the points in the target area, and the arithmetic processing unit 305 in the treatment planning apparatus based on the irradiation direction stored in the memory 304 and the information in the body based on the CT image. Is calculated.

Similarly, a vector whose elements are dose values at n points in the vital organ 402
The amount of irradiation to each spot
Is expressed by the following (formula 2).

The arithmetic processing unit 305 calculates a matrix A and a matrix B, and then a vector representing the score set for each spot in step 203
The following objective function is generated using

Here, wi ⁽¹⁾ in the first term on the right side of (Equation 3) and wi ⁽²⁾ in the second term are weights corresponding to the respective points, and are operated together with the prescription dose in step 103. It is a value entered by the user. The first term and the second term on the right side of (Equation 3) are also present in the conventional treatment planning apparatus, and are terms for controlling the dose distribution so as to satisfy the prescription dose. The first term on the right side of (Equation 3) is the part that controls the dose in the target, and the closer the dose value at m points is to the prescription dose value p set as the target,
Becomes smaller. The second term on the right side of (Equation 3) is a term for controlling the dose in the important organ, and the dose in the important organ may be a dose that does not exceed the allowable dose l. Θ (di ⁽²⁾ -l) in the second term on the right side of (Expression 3) is a step function, and is 0 if di ⁽²⁾ <l, and 1 otherwise.

The third term on the right side of (Expression 3) is a term that directly controls the irradiation amount to each spot, which is a feature of this embodiment. The lower the ratio of the dose to a spot with a high score S _i ,
Therefore, the amount of irradiation is controlled so as to decrease at a spot where the score S _i is set large, and so that the amount of irradiation increases at a spot where the S _i is set small. Irradiation dose that can reduce the impact of uncertainty on the dose distribution by setting a high score for spots that have a large impact on the dose distribution of treatment planning
Can be searched.

K ₀ represents the importance of the third term. The initial value of K ₀ is automatically set, but can be changed by the operator. Depending on the value of K ₀ , the solution gives priority to either dose distribution control (first and second terms in (Equation 3)) or spot dose control (third term in (Equation 3)). You can choose to get. When the operator sets K ₀ to 0, the third term of (Equation 3) is ignored.

The arithmetic unit 305 repeats the iterative calculation after generating the objective function of (Equation 3) above,
Is the smallest
Explore. Non-Patent Document 1 is a detailed example of specific contents of the iterative calculation.

  When the density change amount around the beam passage path is set as the score and the optimization calculation is performed, it is possible to suppress the irradiation amount to the spot where the density change is large. Therefore, when a positioning error occurs, it is possible to suppress the dose to a spot whose range varies greatly due to the density variation of the passage route, and to reduce the dose distribution in the target area.

  On the other hand, if the degree of presence of important organs on the beam passage path when a range error occurs is set as a score and optimization calculation is performed, it is easy to give a dose to an important organ when a range error occurs It becomes possible to suppress the irradiation amount to the spot. Therefore, it is possible to suppress over-irradiation of important organs due to range errors.

  When the dose is determined by iterative calculation, the treatment planning device 301 calculates a dose distribution using the finally obtained spot position and the dose to each spot. The calculated result is displayed on the display device 303 (steps 206 and 207). The operator confirms on the display device 303 whether or not the designated dose is given to the target region without excess or deficiency (step 106).

  A histogram called DVH (Dose Volume Histogram) is also widely used for confirming the dose distribution to the target area. The treatment planning device 301 calculates the DVH value using the arithmetic processing device 305 and displays it on the display device 303.

  The operator analyzes the dose distribution result using the dose distribution and DVH displayed on the display device 303, and determines whether or not the dose distribution satisfies the target condition (step 107). If the distribution is not desirable, the process returns to step 103 to reset the irradiation conditions. This includes changing the irradiation direction and spot spacing. When the condition is changed, the treatment planning device 301 calculates the spot and the dose according to the operator's instruction, and the new dose distribution result is displayed on the display device 303. When a desired result is obtained, the treatment planning is finished (step 108, step 109). The obtained irradiation conditions are stored in the data server 307 through the network.

  In scanning irradiation, after irradiating a certain amount of beam to a certain irradiation position, stop the beam once, move to the irradiation position to be irradiated next, and then start irradiation again, and while moving the irradiation position There is also a raster system that does not stop beam irradiation. In the above-described embodiment, the spot scanning method has been described. However, even in the raster method, when obtaining the irradiation conditions, it is necessary to set a plurality of irradiation positions in order to perform a discrete calculation, and the radiation treatment planning apparatus of the present invention can perform treatment using the raster method. It can also be applied when creating a treatment plan.

301 treatment plan device 302 input device 303 display device 304 memory 305 arithmetic processing device 306 communication device 307 data server 401 CT data slice 402 target region 403 important organ 501 isocenter 502 radiation source 503 beam center axis 504 isocenter plane 506 point 505 and line Straight line 601 connecting the source 502 Surface 602 perpendicular to the beam center axis One of the pixels 603 obtained by dividing the surface 601 A straight line 701 connecting the center position of the pixel 603 and the radiation source 502 One of the irradiation spots 702 The irradiation spot 701 and the radiation source 502 A line 703, a beam stop pixel 704 of the beam irradiated to the irradiation spot 702. [delta] [mm] pixels on a line 503 below

Claims (3)

In a radiotherapy planning apparatus for creating treatment plan information for performing radiotherapy,
And operator prescribed dose, the irradiation angle and an input device for inputting an arbitrary area, the setting the index representing the demands on the dose inhibiting determined based on the irradiation position of the radiation,
A calculation device that determines irradiation conditions so that a dose distribution calculated based on the prescription dose and the irradiation angle approaches the prescription dose, and creates treatment plan information , and
A display device for displaying the treatment plan information;
The calculation device calculates and sets the index from the CT value of the CT data of the irradiation target, and then the index for each irradiation position is changed with respect to the irradiation position included in the arbitrary region of the irradiation target. Then , an objective function that quantifies the deviation between the prescription dose and the irradiation dose using (Equation 4).
And determining the irradiation condition based on the objective function,
In (Expression 4), m is the number of points set in the target region, n is the number of points set in the important organ in the target region, k is the number of spots, p is the prescription dose, and w _i ⁽¹⁾ and w _i ⁽²⁾ are weights corresponding to the respective points, d _i ⁽¹⁾ is a dose value at each point, l is an allowable dose in the important organ, and d _i ⁽²⁾ is at each point. Dose value, K ₀ is the importance of the third term on the right side in (Equation 4), S _i is the index, x _i is the dose at spot i,
Θ (d _i ⁽²⁾ −l) in (Equation 4) is a step function, 0 if d _i ⁽²⁾ <l, and 1 otherwise. apparatus.   The radiotherapy planning apparatus according to claim 1, wherein the arithmetic device determines the index based on the irradiation position and density information.   The radiotherapy planning apparatus according to claim 1, wherein the arithmetic device displays information on the set index.